The functional severity of a stenotic lesion in an artery can be assessed by measuring the pressure gradient across the lesion. Intravascular pressure measurement, particularly in the coronary arteries, has gained widespread acceptance as a tool for guiding catheter-based interventional procedures. Angioplasty or stenting of lesions in coronary arteries can be avoided if the fractional flow reserve (FFR), defined as the ratio of the blood pressures measured distal to and proximal to a lesion after injection of a vasodilating drug, exceeds a certain clinically defined threshold.
Various devices have been developed for sensing arterial pressure at the tip of miniature catheters during medical diagnostic and interventional procedures. The most widely used device of this type, often referred to as a “pressure wire,” employs an electronic pressure transducer embedded in the side of a long metallic tube through which electrically conducting wires pass to a connector at the proximal end. Typically, the transducer is mounted at a distance 1-2 cm proximal to a spring at the distal tip of the tube. The operator navigates the tube through the artery manually until the transducer reaches the desired location for local pressure measurement.
One drawback of electronic pressure measurement systems is the relatively large minimum diameter of the pressure wire, which is determined by the size of the transducer, wires, and wire attachment assembly. The diameter of a pressure wire is critically important, because it must pass through narrow stenoses in blood vessels without significantly increasing the pressure gradient across the stenosis or preventing passage of the wire through the stenosis. This is especially significant because diseased arteries that are candidates for angioplasty, for example, can have lumen diameters smaller than 1 mm.
A second drawback of electronic pressure monitoring systems is their susceptibility to electrical interference and calibration drift. Careful sealing of the wires and transducer to avoid moisture intrusion and shielding of the wires against electromagnetic interference are required to minimize environmental disturbances.
Frequently, acquisition of intravascular images and measurement of intravascular pressures during a single medical procedure is desirable. However in such an application, when intended to be used with imaging catheters, electronic pressure wires, because of their wire connections, are difficult to integrate with intravascular imaging catheters.
The present invention addresses these issues.